george w



'UNITED .STATES PATENT @einem f To WILLIAM' GEORGE W. SYKES, OF MERCER, PENNSYLVANIA,.ASSIGNOR OF E. AMCKELVY, OF PITTSBURG, PENNSYLVAN ON E-HALF sees-seeme- SPECIFIOATIN forming part ofLetters Patent No. 621,177,

dated March 14, 1899.

Application filed November 19, 1898.y Serial No. 696,892. (No model.)

STO au whom it` may concern:

l., zeer,- inthe county of S Be it known that I, zcitzen of theUnited S GEORGE W. SYKES, a tates, residing at Mer- Mercer and State of have invented or discovered a Rensylvane,

Improvement in Protractors,

new and useful of which the following is a full, clear, and extractor.

. egual subdiwsionsand .shcon-ing the locking" .-compauying drawin 'act description, reference being had to theacgs, forming part of this specification, in Which- Figure 1 is a face View of my improved pro- Fig. 2 is a detail view of a modified constructiomon an enlarged scale, illustrat- -ing more fully the extended arm and the devioeforsecuringthelimbatanyposition. Fig. 3. is a detail view' illustrating a modified form wmzemrlesine a earned edgemseeure A device withdrawn.

yMyinvention relates to protractors; and it consists in means whereby the users of such devices areenabled to easily and quickly subdivide the degrees of a circle into minutes with butvone setting of the instrument. Grdinarily such subdivisions are made by the use of avernier-scale, requiring a separate setting -for each reading of the instrument and causing considerable trouble, tiring of the eyes,

, ple, expeditious, and accurate.

circular base of the usual divisions lnto degrees.

eferringnow to the drawings, 2 is the semia protractor provided with To the center of the base, at 3, is pivoted a radial limb 4, at any convenient point of which is located an indicatingfpoint 5, coinciding with the medium line of the limb and from which line all subdivisions are made. In the detail views shown in Figs. 2 and 3 this point 5 is replaced by a locking device of any convenient character, such' as a sliding dog 6, provided with teeth adapted to engage similar recesses in the periphery of the protractor, corresponding to degrees, so that ywhen the dog is withdvawn and inserted in the next space the movement will correspond to one degree. The dog 6 is provided with a thumb-piece 7, by which it may be retracted, and a pressurespring 8 tends to counteract outward pressure and to reinsert the teeth, while suitable guiding devices assist to keep it in alinement.

The 'portion of the instrument which constitutes the invention is gral with and constituting an extension of the radial limb. The edge lO of this arm, which may be curved or straight, is Vsulliciently deflected from lalinement with the medium center a a to correspond to exactly one degree on the protractor between the ex` tremities b c of vthe arm or to any predeterparticular feature of the present an extended arm 9, formed inteter mined subdivision, may be desired. It is obvious also that the length of such arm between the points Z2 and c may be subdivided so as to correspond to the second subdivisions of a degree` and by laying 01T any predeterm'ie eading'ih divisions on the arm 9 in addition to the already determined number of degrees the line of the angle may be at once described Without further movement of the instrument.

It will be seen that in the case of an arm having a straight edge the subdivisions will grad uall yincrease toward its extremity owing tothe divergence of the radiallines of measurement, whereas by intersecting `such lines by cross-lines at regular even distances the 'intersections willdescribe a curved line, to

which lline the' ed form, as in Fig. visions, although either ge may be made to conconstruction will be 3, thus giving even subdi found to be equallyaccu rate and satisfactory. y

The advantages of my invention will be appreciated by the skilled engineer and it will be found applicable to a Wide variety of use by users of this class of instruments.

The construction of the locking device or point-indicator may be varied within the scope of my invention, and I do not de'sire to be limited to the construction shown, but to include such variations or modifications thereof as will suggest themselves to theeskilled mechanic.

Whatl claim is l. A protractorprovided with a pivoted radial limb and an extended arm having an edge .deiiected from the'4 radial line and pros,

vided with subdi visions, substantially as set forth.

IDD

2. A protractor provided with peripheral ln testimonywhereoi have hereunto sei;-

teeth corresponding to the degrees of the. oirmy hand. cle, a radial limb pivoted at the center of the protraotor, a setting device for locating the W SYKES 5 limb, and am extendecl arm bearing a scale Wityneses: Y

for indicating subdivisions of a single degreel, 5C. M. BROWN, substantially asset; forth. W.v EL ilfloKimLvY` 

